| TDF ALS162 time code transmitter | |
|---|---|
 The 350 m tall low frequency antennas of ALS162 time signal in Allouis | |
| Location | Allouis longwave transmitter, Allouis, France |
| Coordinates | 47°10′10″N 2°12′17″E / 47.1695°N 2.2046°E |
| Elevation | 129 m (423 ft) |
| Operator | TéléDiffusion de France on behalf of the ANFR and LNE–SYRTE |
| Frequency | 162 kHz |
| Power | 800 kW |
| Began operation | July 1980 |
| Official range | 3,500 km (2,175 mi) |
ALS162 is a French longwave time signal and standard-frequency radio station and is used for the dissemination of the Metropolitan French national legal time to the public. TéléDiffusion de France broadcast the ALS162 time signal, provided by LNE-SYRTE[1] and LNE-LTFB time laboratories under ANFR (state body for radio frequencies) responsibility, from the Allouis longwave transmitter at 162 kHz, with a power of 800 kW.[2]
The current time signal is generated by extremely accurate caesium atomic clocks and phase-modulated on the 162 kHz (1850.5707284 m wavelength) carrier signal in a way that is inaudible when listening to the signal using normal Longwave receivers. The ALS162 phase-modulated time signal service requires a more complex receiver than the popular German DCF77 amplitude-modulated time signal service, but the much more powerful transmitter (16 times DCF77's 50 kW) gives it a much greater range of 3,500 km.
The signal transmission is almost continuous, but there is a regularly scheduled interruption for maintenance and tests every Tuesday from 08:00 to 12:00.[3]
The transmitter building contains two caesium atomic clocks which are used to generate the time signal and which are monitored through the SYREF system and GPS common-view measurements, to align with the official French UTC(OP) time scale. The ALS162 time signal exactitude should be in excess of 1 millisecond uncertainty.[4] The monitoring of the ALS162 signal is jointly conducted by LNE-SYRTE, LNE-LTFB and the trade body France Horlogerie and measurement results are published in real time.[1] Monthly monitoring bulletins, like H 649 of the ALS162 signal regarding January 2022 measurements, show if the exactitude goals were met.[5] The time signal is critical for over 300,000 devices (clocks in public places, information panels, traffic lights, public lighting, parking meters, etc.) deployed within French enterprises and state entities, such as French Railways (SNCF), electricity distributor Enedis, airports, hospitals, municipalities, etc. which depend on the signal in France and abroad.[6][1][7]
- ^ a b c Provision of the legal time by ALS162 signal
- ^ ANFR website
- ^ "Les tests du signal horaire" [The tests of the time signal] (in French). Agence Nationale des Fréquences. Retrieved 2017-03-16.
- ^ LNE-SYRTE ATTESTATION Exactitude du signal ALS162 (in French)
- ^ Observatoire de Paris LNE-SYRTE, Bulletin H 649, janvier 2022, 1.2 Mesure de la porteuse et mesure de temps du signal ALS162 (in French)
- ^ (in French)L'émetteur d'Allouis passe aussi à l'heure d'été cette nuit
- ^ Brulhatour (21 December 2016). "Le signal horaire restera sur le 162 kHz de France Inter". La Lettre (in French). Editions HF. Retrieved 14 January 2020.